Cibctiit connections of electron-discharge apparatus



w. 0. WHITE. CIRCUIT CONNECTION 0F ELECTRON DISCHARGE APPARATUS.

APPLICATION FILED AUQ.23, I915.

Patented Aug. 22, 1916.

Fig. I.

, Inventor Wi|lia'mC.White, b5

I-lis Attorney.

UNITED STATES PATENT OFFICE.

WILLIAM C. WHITE, 01 SCHENECTADY, NEW YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, l CORPORATION 01' NEW YORK.

CIRCUIT CONNECTIONS OF ELECTRON-DISCHARGE APPARATUS.

specification of Letters Patent. Patented Aug. 22, 1916.

Application filed August 88, 1915. I Serial No. 48,770.

connections for electron discharge apparatus rent for vanode or the and more especially electron discharge apparatus of the type in which a filamentary cathode inclosed in an evacuated envelop is provided with means for heating to incandescence to cause it to emit electrons which may serve to conve negative electricity to a cooperating ano e inclosed in the same envelop. Such devices may be used for producing X-rays or rectif ing alternating current or, when provide with a controlling grid, for amplifying variable currents, detecting wireless signals and for various other purposes.

It has been customary prior to my invention to provide for heating the cathode a direct current source such as a battery or di-' rect current generator. I The external circuit connections to the cathode have been made to one sideof the filament and as a result all parts of the filament have not been at the same potential with respect to the grid, the difference between extreme ends being equal to the potential .i'mpressed upon thefilament. Where a source of direct current is employed, this difierence of potential is constant and therefore, will not reduce variations in the operation of the evice. It is, however, more convenient in many cases to employ an alternating curheating the filament, and, when this is done and the connections made to one side of the filament, which are thereby introduced may seriously affect the efiicient operation of the device.

The object of my invention is to provide an improved circuit connection for electron discharge devices whereby alternating current may be employed for heating the filament and the disadvantage above mentioned, as well as o hers which will hereinafter appear, may be overcome.

. nected directly thereto,

' charge relay comprisin the potential variations v primary circuit In the practical application of my invention, current for heating the filament is obtained from the secondary of a transformer and the connections from anode and grid to the cathode are made to the middle point of the secondary winding. When the connections are made in this way the average difference of potential at any instant between different portions of the cathode and the grid and anode, due to the heating current, will be zero.

My invention will best be understood by reference. to the following description taken in connection with the accompanying drawing in which- Figu mitting wireless signals in which the filament of the electron discharge device is supplied with alternating current and in which my invention may be employed to advantage; and Fig. 2 shows a different transmitting system in which a source of alternating current is utilized for other purposes as well as heating the cathodes of the various electron discharge devices used.

In the organization illustrated in Fig. 1, the antenna 1 is grounded as usual and has connected thereto a source of high frequency oscillations which in this case consists of a high fre uency alternator 2. This may be inductive y connected to the antenna by means of the transformer 3 or may be conif desired. An inductance 4 which may be varied to tune the antenna circuit to the desired frequency may be placed in series with the antenna. An energy consuming device 6 which, in the present case, consists of an electron disan exhausted envelop containing an an e 7, a cathode Sand a conducting grid shaped body 9 interposed between the cathode and anode is connected to two oints in the antenna circuit between which t ere is normally a large difference of pptential. In the present case it is connected tween the point 5 in the antenna and grou d. The cathode 8 isof filamentary orm prefera bly of tungsten, and is provided-with current for heating it to incandescence by the secondary 10 of the transformer 11 which may be supplied with alternating current from the mains 12. The temperature of the cathode may be adjusted by means of a variable resistance 13 in the of the transformer.

The no transformer 15 may connection between the cathode of"tliis device and ground is -brought to the point 14 which is the middle point in'the winding of the secondary 10.

through the secondary of the transformer 15 and battery 16. The primary circuit of the transformer 15 includes a tele hone transmitter 17 with local battery 18. second circuit consisting of the condenser 19 and the variable inductance 20 is provided between the grid 9 and cathode 8. In the operation of this system to secure the best possible results it will usuall be found desirable to adjust the current fibwing through relay 6 so that about one-half of the energy of the source 2 is normally divertedfrom the antenna circuit. This may be done by adjusting the potential impressed upon the grid 9 by the battery 16. In order that the currents produced in the secondary of the flow through the battery 16, condenser 21 may be inserted in shunt to this battery.-

When sound waves act upon the transmitter '17 potential variations are set up in the secondary of the transformer 15 and the potential of the grid 9 is thereby varied in accordance with the variations in the sound waves. As a result the amount of energy which is diverted from the antenna through relay 6 is varied accordingly and there is a corresponding variation in the energy radlated from the antenna.

In the preferred construction of the electron discharge relay 6, the anode 7 is made up of one or more plates of considerable area and the grid 9 consists of a number of turns of fine wire wound on a supporting frame work and located in parallel relation to the anode plate or plates. The cathode 8 is alsopreferably locatedin a plane parallel to the grid and anode. The distance between these members is preferably small and as a result there is an appreciable capacity between them. It will be seen that with the arrangement indicated the anode 7 is alternately positive and negative with respect to the cathode and that as aresult the grid 9 will have induced thereon by electrostatic induction positive and ne ative charges. Although the grid and cathode are connected electrically reversals in polarity in the induced charges are so rapid that the potential difference between the two at times may become very lar e, the secondary of the transformer '15 o flow of high frequency charging current between the grid and cathode. As a result the positive potential which may be induced on the grid 9 when the anode is also positive maybecome so great as to allow enough current to flow through the relay 6 to divert from the antenna nearly all of the energy from the high frequency source, even when A second connection to this same point is made from the rid 9 not be compelled to ering high impedance to the no potential is induced upon the grid by means of the telephone transmitter. Also the potentials induced by the secondary of the transformer 15 are in most cases small in comparison to this induced potential and hence will produce little variation in the current flowing through the relay 6. In order to overcome this diiiiculty the circuit comprising the condenser 19 and inductance 20 is tuned to the frequency of the source 2 so as to serve as a short circuit between grid and cathode for these induced charges.

In case the connection the cathode through'the secondary of transformer 15 were made to one end of the secondary 10 which supplies current for heating the filament the difference of potential between the opposite end of the cathode and the grid would fluctuate by an amount equal to the filament voltage. As a result there would be a corresponding variation in the amount of energy diverted from the antenna. That is, in addition to the variations produced by the action of the sound waves there would be variations having a frequency e ual to that of the source supplied to trans ormer 11. These variations of course would impair the transmission of the desired signals. This difliculty however is overcome by connecting the grid to the middle point of transformer 10 thereby neutralizing the effect of any differences of potential between grid and filament due to the potential alternations of the source used for heating the filament. The amount of energy diverted from the antenna also depends upon the difference of potential between the anode and cathode and with'the connection from anode to cathode. Made to one side of the filament there wouldbe the same variafrom the grid to a tion in potential between anode and cathode I as between cathode and grid. This difliculty 1s also overcome by connecting the anode to the middle point of secondary 10.

In the system illustrated in Fig. 2', electron discharge device 6 is employed to produce continuous waves in the antenna 1. In order to accomplish this, anode 7 and cathode 8 are connected to a source of direct current which is obtained by rectifying alternating current from the source 22 which supplies transformer 23, the secondary turns of which are subdivided to give different voltages. One group 10 of the, secondary turns provides current for heating cathode 8. Current for is derived from the secondary turns between points 24 and 25,,electron discharge rectithe plate circuit of device 6 fiers 26 and 27 being employed to rectify the I alternating current. The group of second" ary turns 28 provides current for heating I the cathodes of these rectifiers. Connection to cathode 8 is made between a neutral omt 29 in the transformer secondary an the middle point of 'group 10 of secondary turns. 0

A connection is also provided from the anode 7 to the cathodes of rectifiers 26 and 27 through inductance 30 and the secondary of transformer 31 to the middle point of group 23. The inductance 30 is inductively related to the inductance 3:: in the antenna The circuit, which includes the cathode 8 and the grid 9, contains an inductance 33 which is coupled to a second inductance 34 in the antenna. The coupling between 30 and 32 is preferably close, while that between 33 and 34 may in some cases be made very loose. The circuit which comprises the direct current source of supply, the inductance 30, the cathode 8 and anode 7, for convenience of description I designate the plate circuit. The circuit which comprises the grid 9, inductance 33 and cathode 8, I designate the grid circuit. \Vith this arrangement, when current starts to flow in the plate circuit, potential is induced in coil 32 and in the antenna. This produces a corresponding induced potential in coil 33 and varies the potential of the grid 9. This change in grid potential in turn produces a variation in the current in the plate circuit. \Vlien the potential produced in the grid circuit causes the grid to become more negative the current flowing in plate circuit is decreased while an induced potential which makes the grid more positive increases the current flow in the plate circuit. These variations in the current in the plate circuit produce an alternating current in the antenna, the frequency of which will be the same as the frequency to which the antenna is tuned. The amplitude of the high frequency waves thus produced in the antenna will, among other things, depend upon the potential of the direct current source and will be constant as long as this potential is constant and other conditions also remain unchanged but their amplitude will vary in accordance with any variations in potential supplied to the plate circuit. In order to vary the amplitude of these waves in accordance with sound waves, potential variations corresponding to those set up in the secondary of transformer 15 are impressed upon the plate circuit. The potential variations in the secondary of transformer 15 are in the present case amplified by a second electron discharge device 35 similar in structure to device 6. This is done by impressing the potential variations upon the grid 36 of device 35. The amplified potential variations thereby set up in the plate circuit of device 35 are impressed upon the plate circuit of device 6 by means of the transformer 31. A direct potential for the plate circuit of device 35 is obtained in the same manner as for device 6. In the operation of this particular system, I have found it desirable to employ a higher voltage for device 35 than for device 6. To provide this higher voltage, a larger number of secondary turns of the transformer are utilized and rectificrs 37 and 38 are connected to points 39 and 40 respecti ely. The group of secondary turns 41 provides current for heating the cathodes of these rectifier Connection is made from point 29 to the middle point of group 42, which provides current for heating cathode 43 and from the anode 44 of device 35 to the cathodes of rectifiers 37 and 38 through the primary of transformer 31 to the middle point of group 41. Condensers 45 and 46 may be employed to smooth out the variations in potential of the rectified current supplied to devices (3 and 35 and condenser 47 to provide a shunt path forthe high frequency component of the current in the plate circuit of device 6 around the secondary of transformer 31. Vhen high frequency variations of current are occurring in the plate or grid circuits of the difi'erent devices, this current passes through the central taps of the transformers to the filaments without undue impedance, and divides equally between the two legs of the filament loop, as the inductance of the two sides of the winding is neutralized.

While I have described the application of my invention to only two systems for transmitting wireless signals, it will be apparent to oiie skilled in the art that it will be of utility in many other organizations in which electron discharge devices are employed, for wireless signaling or other purposes, and that numerous applications thereof may be made without departing from the scope of the appended claims.

\Vhat I claim as new and desire to secure by Letters Patent of the United States is 1. The combination with an electron dis charge device comprising an evacuated envelop having therein a filamentary cathode and a cooperating anode of a source of alternating potential applied to said cathode for heating it to incandescence and external circuit connections between said cathode and anode so arranged that the average potential difference between cathode and anode at any instant is independent of the potential applied to the cathode for heating purposes.

2. The combination with an electron discharge device comprising an evacuated envelop having therein a filamentary cathode and a cooperating anode of a transformer connected to a source of alternating current and having its secondary connected to said cathode for heating it to incandescence and an external circuit connection between said anode and the central point in the secondary winding of said transformer.

3. The combination with an electron discharge device comprising an evacuated envelop having therein a filamentary cathode, a cooperating anode, and a dischar e controlling grid, of a source of alternating potential applied to said cathode for heating it to incandescence and external circuit connections between said cathode and anode and between said cathode and grid so arranged that the average potential difference between cathode and anode and between cathode and grid at any instant is independent of the potential applied to the cathode for heating purposes.

4. The combination with an electron discharge device comprising an evacuated enand a discharge controlling grid of a source of alternating potential applied to said cathode for heating it to incandescence and external circuit connections between said cathode and grid so arranged that the average potential difference between cathode and grid at any instant is independent of the otential applied to the cathode for heating purposes.

6. The combination with an electron discharge device comprisin an evacuated envelop having therein a lamentary cathode and a discharge controlling grid of a transformer connected to a source of alternating current and having its secondary connected to sald cathode for heating it to Incandescence and an external circuit connection from said grid to the central point in the secondary winding of said transformer.

In witness whereof, I have hereunto set my hand this 20th day of August, 1915.

WILLIAM 0. WHITE. 

